def next_bigger(n):
    digits = list(str(n))
    digits.sort(reverse=True)
    greatest_number = int("".join(digits)) 
    if greatest_number == n:
        return -1
    
    for i in range(n+1, greatest_number+1):
        greater_number = list(str(i))
        greater_number.sort(reverse=True)

        if greater_number == digits:
            return i

print(next_bigger(12))